A Prescription NeoLucida

Do you wear glasses? It’s possible you may prefer a “Prescription NeoLucida”.

It can be difficult to use a camera lucida if you also need to wear glasses. One major problem is that there’s not much room for glasses between your eye and the NeoLucida eyepiece, given the 25mm recommended viewing distance:

But even if you could fit your glasses in that narrow space, you wouldn’t necessarily want to. Camera lucidas require you to focus at two distances simultaneously: Firstly, at your pencil and paper (perhaps 30cm from your eye); and secondly, at your subject (perhaps 100cm for a portrait, or even 5000cm for a landscape). Whether you’re nearsighted or farsighted, one of these will be annoyingly out-of-focus. That’s what this hack addresses.

This page describes a quick hack for (more-or-less permanently) modding your NeoLucida so that it best suits your imperfect vision! It will take about ten minutes, plus a 24-hour curing period. You’ll need:

Sugru is pretty amazing stuff — a favorite fix-it substance for Makers around the world. It’s a self-setting rubber that can be formed by hand. It moulds like play-dough, bonds to almost anything, and turns into a strong, flexible silicone rubber overnight. One 5-gram package (which is all you’ll need) costs about $3.

So here’s the basic idea: pop one of the lenses out of your old glasses, and adhere it to your NeoLucida with the Sugru. This is basically a permanent operation, so you won’t want to do this if you share your NeoLucida with someone else, or if you expect your eyeglass prescription to change a whole lot. If you’d prefer a temporary fix instead, consider this design to attach your lens using binder clips.

Here are the basic steps for this hack:

Determine which is your dominant eye; remove that lens from your old glasses.

Determine which orientation (lefty/righty) of the NeoLucida works best for you.

Determine whether the lens should be positioned in front of, or under, the NeoLucida.

Adhere the lens to the NeoLucida.

STEP 1. Determine which is your dominant eye.

Which eyeglass lens should you use: the left one or the right one? To answer this, it’s important to figure out your “eye dominance“, also called “ocular dominance” or “eyedness”. Just as you have a dominant hand for writing and drawing, you also have a dominant eye for viewing. Perhaps you already know this — it’s simply the eye you prefer to use with the NeoLucida, after all! But there are also eye dominance tests to help you figure it out. Here are three of the most popular, from Wikipedia:

The Miles test: The observer extends both arms, brings both hands together to create a small opening, then with both eyes open views a distant object through the opening. The observer then alternates closing the eyes or slowly draws opening back to the head to determine which eye is viewing the object (i.e. the dominant eye).

The Porta test: The observer extends one arm, then with both eyes open aligns the thumb or index finger with a distant object. The observer then alternates closing the eyes or slowly draws the thumb/finger back to the head to determine which eye is viewing the object (i.e. the dominant eye).

The Dolman test (also known as the hole-in-the-card test): The subject is given a card with a small hole in the middle, instructed to hold it with both hands, then instructed to view a distant object through the hole with both eyes open. The observer then alternates closing the eyes or slowly draws the opening back to the head to determine which eye is viewing the object (i.e. the dominant eye).

Incidentally: approximately two-thirds of people are “right-eyed”, and one-third are “left-eyed” — and there is no relation to whether you are left-handed or right-handed.

Once you know which eye you prefer to use with the NeoLucida, pop out the corresponding lens from your disused pair of glasses.

STEP 2. Determine which orientation of the NeoLucida works best for you.

The NeoLucida’s eyepiece is removable, and allows two different orientations. You’ll need to decide which of these are more comfortable. This will depend on your eye dominance, your handedness, and even the size of your nose! We recommend you set up the NeoLucida clamped to a table, and try using it with both configurations. Pay attention to whether your nose bonks into the eyepiece, and/or whether your drawing-hand bonks into the clamp and gooseneck post.

STEP 3. Determine how you prefer to position the lens on the NeoLucida.

If you have difficulty seeing far away (“nearsighted”), you’ll probably want to position the lens in front of your NeoLucida’s eyepiece, between the prism and your subject. Here’s a photo of a completed modification for a nearsighted person, with the lens in this position:

On the other hand, if you have difficulty seeing things that are close (“farsighted”), you’ll probably want to position your lens under the NeoLucida eyepiece, between the prism and your paper. If you’re not sure which is best, try the lens in both positions and see what works best.

Note: this modification may not work well for people with very significant astigmatisms (cylindrical imperfections of vision). If you have a strong astigmatism, you’ll need to be very precise about how you orient the lens with respect to the prism.

STEP 4. Adhere the lens to the NeoLucida.

We recommend Sugru self-modeling rubber, but there are actually lots of different kinds of putties, glues and other modeling materials you could use to attach your lens to the NeoLucida eyepiece. For example, we’re also huge fans of Shapelock, a low-temperature, hand-moldable thermoplastic. Shapelock is available from the Maker Shed and Amazon, and (from another manufacturer) is also known as InstaMorph.

If you’re using Sugru to adhere the lens to the NeoLucida eyepiece, be sure to follow the Sugru instructions carefully. In particular, make sure your hands, lens and eyepiece are clean and free of any oils, and be sure to give the Sugru the recommended 24-hour curing time.

When attaching the lens to the eyepiece, we recommend you consider the following:

Be sure to keep the Sugru (or other glue) away from the circular thumb-nut. The thumbnut is useful for adjusting the orientation of the eyepiece, and shouldn’t be glued in place.

Decide whether you want to cover or discard the eyepiece endcap. We removed our endcap entirely, in order to get a better bond between the Sugru and the eyepiece. That’s OK.

Good luck! If you make this mod, please send us photos at info@neolucida.com!